FIG. 1 shows a relay node (RN) 120 and User Equipments (UEs) 131 and 132 located in an area of one base station (or eNodeB or eNB) 110 in a radio communication system 100. The RN 120 may transmit data received from the eNodeB 110 to the UE 132 located in an RN area and transmit data received from the UE 132 located in the RN area to the eNodeB 110. In addition, the RN 120 may expand a high data rate area, improve communication quality in a cell edge, and support provision of communication in a building or in an area other than a base station service area. In FIG. 1, the UE 131 (hereinafter, referred to as a macro-UE or M-UE) which directly receives a service from the eNodeB and the UE 132 (hereinafter, referred to as a relay-UE or R-UE) which receives a service from the RN 120 are shown.
A wireless link between the eNodeB and the RN is called a backhaul link. A link from the eNodeB to the RN is called a backhaul downlink and a link from the RN to the eNodeB is called a backhaul uplink. In addition, a wireless link between the RN and the UE is called an access link. A link from the RN to the UE is called an access downlink and a link from the UE to the RN is called an access uplink.
In a general radio communication system, only one carrier is mainly considered even when the bandwidths of the uplink and the downlink may be differently set. For example, a radio communication system in which the number of carriers configuring the uplink or the downlink is 1 and the bandwidth of the uplink and the bandwidth of the downlink are generally symmetrical to respect to each other may be provided based on a single carrier.
International Telecommunication Union (ITU) has requested candidate technologies of the IMT-Advanced to support an extended bandwidth, compared with the existing radio communication system. However, it is difficult to allocate a frequency having a large bandwidth in the whole world excluding some regions. Accordingly, as technologies of efficiently using a plurality of small bands, carrier aggregation, bandwidth aggregation or spectrum aggregation technologies of physically aggregating a plurality of bands in a frequency domain so as to logically obtain the same effect as the use of a large band have been developed. The carrier aggregation technology may be also called multi-carrier technology.
The carrier aggregation technology is introduced in order to increase throughput, to prevent cost increase due to introduction of a wideband RF element, and to guarantee compatibility with the existing system. The carrier aggregation technology refers to technology of exchanging data between a UE and an eNodeB by aggregating a plurality of carriers in a bandwidth unit defined in the existing radio communication system (e.g., a Long Term Evolution (LTE) system in case of an LTE-A system or an IEEE 802.16e system in case of an IEEE 802.16m system). A carrier of the bandwidth unit defined in the existing radio communication system may be called a Component Carrier (CC). For example, the carrier aggregation technology may include technology of supporting a maximum system bandwidth of 100 MHz by aggregating a maximum of five CCs even when one CC supports a bandwidth of 5 MHz, 10 MHz or 20 MHz. The carrier aggregation technology may be applied to the uplink and the downlink and may have a symmetric or asymmetric configuration in the uplink and the downlink. The carrier aggregation (or multi-carrier) technology may be applied to the backhaul link between the eNodeB and the RN and/or the access link between the RN and the UE.